19.7 Blood Presssure Flashcards
Highest in aorta
Pressure results when flow is opposed by resistance
Pumping action of heart generates blood flow
High –> Low pressure (decreases as vessel gets smaller)
Systemic blood pressure
Determined by two factors:
1. Elasticity of arteries near heart
2. Volume of blood forced into them at any time
Arterial blood pressure
Blood pressure near heart
Rises and falls with each heartbeat
“Stretches then relaxes”
Pulsatile
Pressure exerted in aorta during ventricular contraction
Left ventricle pumps into aorta, stretching it
First sound when when taking pressure (around 120 mmHg)
Systolic pressure
Lowest level of aortic pressure when heart is at rest
Sound disappearing when taking pressure (around 70-80 mmHg)
Diastolic pressure
Difference between systolic and diastolic pressure
Pulse pressure phases out near ends of arterioles
Can be felt as a pulse
Pulse pressure
Caused by rhythmic expansion and contraction of arteries due to heart contraction
What we hear when taking blood pressure
Pulse
Pulse and blood pressure, respiratory rate and body temperature
Vital signs
Most routine spot to measure pulse
Radial pulse
Areas where arteries are close to body surface
Can be compressed to stop blood flow in event of hemorrhaging
Pressure points
pressure point list
Blood pressure gauge
Sphygmomanometer
Average pressure in a patient’s arteries during one cardiac cycle
Pressure that propels blood to tissues
Between 70-100 mmHg
Mean arterial pressure
True or false. The heart spends more time in diastole
True
Lower pressure desirable to avoid rupture
Ranges from 35 (start) to 17 mmHg (end)
Capillary pressure
Changes very little during cardiac cycle
Small pressure gradient, only about 15 mmHg
Venous pressure
Contraction of skeletal muscle “milking” blood back toward heart
Valves prevent backflow
________ pump
Muscular pump
Pressure changes during breathing move blood towareds heart by squeezing abdominal veins as thoracic veins expand
__________ pump
Respiratory pump
Under sympathetic control, smooth muscles constrict, pushing blood back towards heart
Sympathetic venoconstriction
What are the three factors regulating blood pressure?
- Cardiac output
- Peripheral resistance
- Blood volume
Neural controls
Hormonal controls
Renal controls
3 things that affect major factors
Condition where blood vessels inadequately fill and cannot circulate blood normally
“Shocking” to the body
Circulatory shock
Results from large scale blood loss
Hypovolemic shock
Results from extreme vasodilation and decreased peripheral resistance
Not enough oxygen for lungs
Vascular shock
Results when an inefficient heart cannot sustain adequate circulation
Cardiogenic shock
Sustained elevated arterial pressure of 140/90 or higher
“Silent killer”
Doesn’t show signs for 10-20 years
Hypertension
Heart works harder
Accelerates atherosclerosis
Makes tunica media thicker
Myocardium thickens and weakens
Prolonged hypertension
No underlying cause identified
90% of hypertension cases
Primary hypertension
Less common form of hypertension
Due to identifiable disorders such as:
Kidney disease
Obstructed real arteries
Endocrine disorders
Secondary hypertension
Low blood pressure (90/60)
Not a concern unless it causes inadequate blood flow
Hypotension
Blood flow through body tissues; Involved in oxygen delivery, gas exchange, absorption of nutrients, urine formation
Tissue perfusion
Sympathetic nervous system and hormones control blood flow through whole body
Extrinsic control
Autoregulation; Local conditions that regulate blood flow to that area
Local arterioles feed capillaries can undergo modification of their diameters
Intrinsic control
Fastest in aorta, slowest in capillaries, then increases in veins
(Allows for exchange between blood and tissues)
Velocity of blood flow
Where fluid is forced out of in capillary
Arterial end
Where blood is returned in capillary
Venous end
Force exerted by fluid pressing against wall (boundary)
Due to blood pressure
Hydrostatic pressure (HP)
Capillary blood pressure that tends to force fluids through capillary walls
Greater in arterial end
Capillary hydrostatic pressure (HPc)
Abnormal increase in amount of interstitial fluid
Aka swelling
Edema
Excess interstitial fluid in subcutaneous tissues
Swollen feet images
Pitting edema
Pressure pushing fluid back into vessel
Usually assumed to be 0
Interstitial fluid hydrostatic pressure (HPif)
Force opposing hydrostatic pressure
Created by large non diffusible molecules that are unable to cross capillary wall
Encourage osmosis
Colloid osmotic pressure (OP)
Created by non diffusible plasma proteins pulling water back into capillary
About 26 mmHg
AKA - oncotic pressure
Capillary colloid osmotic pressure (OPc)
Comprises all forces acting on capillary bed
Net filtration pressure (NFP)
Net fluid flow out arterial end
Positive NFP
Filtration
Net fluid flow in at venous end
Negative NFP
Reabsorption
True or false. Plasma is half total blood volume?
True
Due to non diffusible solutes that cannot cross the boundary
Osmotic pressure
(Hpc + OPif) - (HPif + OPc)
Net reabsorption
